refactor(linkedin-studio): S30 magnitude-scrub (discrete-% class) — unsourced reach/engagement penalties -> SSOT

Hardening-class, NOT re-hardening: surgical SSOT-reconciliation of discrete percentage
penalties/declines stated as fact with no primary source in the SSOT
(references/algorithm-signals-reference.md). Same tool-grounded discipline as S27/S28
(read-and-show -> grep-confirm -> re-grep final). Re-grep surfaced drift + same-class siblings
beyond the plan's stored list; all surfaced and operator-approved before edit.

Scope: the discrete-% reach/engagement-penalty class only. The unsourced "Nx" reach/format
MULTIPLIER class (~50 instances across ~15 files) is a separate, larger pass -> deferred to S31
(operator: run everything, across multiple sessions).

HARDEN (20 edits, 7 files):
- linkedin-formats.md (5): :6 47-50% decline + :7 15%->31% feed-share -> directional; :176
  AI-comment 30%/55% -> ~45% less engagement (correlational, medium); :231/:279 hashtags -68%
  -> diminishing returns, no discrete figure.
- linkedin-growth-playbook (6): :158 47-50% decline (twin of formats:6) + :166 hashtags -68%
  + :224/:225 post-length 25%/32% + :435/:828 posting-frequency 25% -> directional, no
  discrete figure. (:221 1.17x multiplier folded in per operator approval; the rest of the
  multiplier class -> S31.)
- glossary.md (2): :91 engagement-bait -30-50% + :235 topic-gap -15-25% -> "correlate with
  lower reach, no discrete figure".
- engagement-coach.md (2): :195 55% + :455 -30%/-55% AI-comment -> ~45% less engagement
  (correlational), actively suppressed.
- post-feedback-monitor.md (1): :330 -25%/post -> "tends to split your own audience".
- ab-testing-framework.md (1): :66 hashtags -68% -> no discrete figure.
- poll-strategy-guide.md (2): :20 / :205 poll-overuse penalty -> declining effectiveness
  (directional).

KEPT INTACT (operator-locked / different class): engagement-pod + AI-slop suppression framing
(SSOT high-confidence); firsthour:112 (no number); poll:206 / poll:3 (qualitative); growth:567
conversion-rate; formats:268 list item.

VERIFY: discrete-% penalty/decline class re-grep across the 7 files -> NONE; leave-items intact;
bash scripts/test-runner.sh -> Passed 81 / Failed 0 / Warnings 0, exit 0; counts 29/19/26/6 +
v0.5.0 unchanged (.md prose only). Disposition: FIXED (20 edits, 7 files), one atomic commit,
local (push held).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016qgzo6rxthw7KuxHjn5vyE

references/linkedin-formats.md

@@ -3,8 +3,8 @@
 ## Critical Context: The Algorithm Revolution
 
 **The 2025-2026 Shift:**
-- Organic reach declined 47-50% for average users
-- Top 1% of creators: content rose from 15% to 31% of all feeds
+- Organic reach declined sharply platform-wide (directional; exact YoY varies by source — see `references/algorithm-signals-reference.md`)
+- Feed distribution concentrated further toward top creators (directional; no single sourced figure)
 - Algorithm now prioritizes topical authority over everything else
 - Dwell time became the golden metric
 - External links in the body correlate with lower reach (see `references/algorithm-signals-reference.md`)
@@ -173,7 +173,7 @@ The first hour after posting determines 70% of your post's total reach. See the
 4. **Comments <15 words** (Medium signal)
 5. **Reactions** (Lower signal - baseline engagement unit; see `references/algorithm-signals-reference.md`)
 
-**AI-generated generic comments reduce reach by 30% and engagement by 55%**
+**AI-generated generic comments correlate with ~45% less engagement (correlational, medium confidence) and are actively suppressed; no separate sourced reach figure — see `references/algorithm-signals-reference.md`**
 
 ### Dwell Time: The Golden Metric
 
@@ -228,7 +228,7 @@ Algorithm prioritizes content that keeps users on platform longer.
 
 **Current function:**
 - Metadata only, not discovery
-- Use 3-4 relevant hashtags (5+ hashtags = -68% reach)
+- Use 3-4 relevant hashtags (more shows diminishing returns; no primary source for a discrete figure)
 - Focus on keyword-driven SEO throughout content
 - Actual words in your post matter MORE than hashtags
 
@@ -276,7 +276,7 @@ Immediate engagement in first hour is critical for triggering subsequent waves.
 - Compound authority over time
 
 **Hashtag guidance (updated for 2026):**
-- Use 3-4 relevant hashtags (5+ hashtags = -68% reach)
+- Use 3-4 relevant hashtags (more shows diminishing returns; no primary source for a discrete figure)
 - Focus on keyword-driven SEO throughout post
 - Actual words matter more than hashtags
 - Don't rely on hashtags for discovery